{
   my @data = (
      [ qw( abab abab  ) ],
      [ qw( abab abaa  ) ],
      [ qw( abab qrst  ) ],
      [ qw( abab abba  ) ],
      [ qw( abab ababa ) ],
   );

   printf("%-5s -   %-8s is %sOK\n", @$_, (compare(@$_)?'':'not '))
      foreach @data;
}